git.m6w6.name Git - m6w6/libmemcached/blob - libmemcached/murmur_hash.c

   1 #include "common.h"
   2
   3 /*
   4   "Murmur"hash provided by Austin, tanjent@gmail.com
   5 */
   6
   7 #define MIX(h,k,m) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
   8
   9 uint32_t murmur_hash(char *key, size_t length)
  10 {
  11   const uint32_t m= 0x5bd1e995;
  12   const int r= 16;
  13   uint32_t h= length * m;
  14   uint32_t k = 0;
  15
  16   while(length >= 4)
  17   {
  18     k = *(uint32_t*)key;
  19     MIX(h,k,m);
  20
  21     key += 4;
  22     length -= 4;
  23   }
  24
  25   switch(length)
  26   {
  27   case 3: k += key[2] << 16;
  28   case 2: k += key[1] << 8;
  29   case 1: k += key[0];
  30           MIX(h,k,m);
  31   };
  32
  33   h *= m;
  34   h ^= h >> 10;
  35   h *= m;
  36   h ^= h >> 17;
  37
  38   return h;
  39 }